Here are some great pre-CGI (thousands of real extras) war movies (some are not strictly in the war genre, but they all have a large war component):

War and Peace (1966 quadrilogy) - Epic adaptation of the Tolstoy novel. Comes to almost 7 hours, but it's divided into 4 parts so you don't have to watch it all at once. Not strictly in the war genre, but has some of the greatest non-CGI battle sequences.

Waterloo (1970) - Historical epic on Napoleon's final battle and defeat (Chris Plummer plays Wellington while Rod Steiger is Napoleon). Made by the same director as War and Peace, and has similar epic production values (thousands of extras and actual massed cavalry).

Liberation (1970 film series) - Covers the Soviet victories from Kursk to Berlin. Plenty of epic battle shots, with thousands of extras and lots of real tanks.

Battle of Moscow (1984 film series) - Covers the German invasion and immediate aftermath. Same director as Liberation, and similar production values.

Battle of Neretva (1969) - Yugoslav partisan epic about a battle with the Germans, Lots of famous actors like Orson Welles, Yul Brynner, etc. and great non-CGI production values.

Mihai Viteazul/Michael the Brave (1972) - Romanian (communist era) epic on the titular character. Part 1 and Part 2 are on YouTube.

Potop (1974) - Polish film set in the Polish-Lithuanian war against Sweden.

Khan Asparuh (1981) - 3-part Bulgarian nationalist epic on the country's founding. Part 3 has a massive reenactment of the Battle of Ongal.

Link to both films

Lawrence of Arabia (1962) - David Lean's masterpiece on T. E. Lawrence.

Spartacus (1960) - The Kubrick epic starring Kirk Douglas.

El Cid (1961) - A classic Hollywood epic on the medieval Spanish knight, with Charlton Heston and Sophia Loren.

The Longest Day (1962) and A Bridge Too Far (1977) - Hollywood epics on the D-Day Landings (shot far more conventionally than Spielberg's SPR so YMMV) and Operation Market Garden, based on books by Cornelius Ryan. Both movies were filmed in the epic manner and have a lot of stars (literally) like Sean Connery, John Wayne, Anthony Hopkins, Robert Mitchum, and so on.

Dunkirk (1958) - The earlier b&w movie on the subject. Makes a great comparison to Nolan's take on the subject - this one was shot far more conventionally.